The broad class of equipment known as mobile machinery includes machines known as dozers (sometimes called "bulldozers") which have a front-mounted blade for moving and removing earth as well as other materials atop or near the earth surface. Such dozers are sometimes mounted on rubber tires for propulsion. However, urging the dozer blade through the earth requires very high forward force and for that reason, crawler-mounted dozers are in wide use.
Such dozers are propelled by tracks (much like a military tank) and are capable of exerting high forward force on the blade. Such force is possible since the tracks bite into and engage the ground. Track-ground engagement is quite satisfactory for dozer operations and it is sometimes said the track and the ground are "geared" to one another like gear teeth are engaged.
Dozers remove earth in much the same way that a wood plane shaves wood, i.e., by passing a blade across the earth surface and "rolling up" a layer of earth. Such dozers are employed for road construction and to "shape" the exposed surface of the earth to some contour. They are also used to urge earth to one side or the other of the dozer's travel path rather than merely to push earth straight ahead.
The dozer operator is able to raise or lower the blade and to "skew" it left or right. It is this latter capability which permits earth to be urged to one side or the other. And the operator can also tilt the blade so that one end is higher than the other.
In one known arrangement, the dozer blade is mounted somewhat forward of the tractor engine compartment and is attached at two locations, one near the top and one near the bottom of the blade, about midway between the blade ends. More specifically, the lower attachment point is by a pivot assembly coupling the blade to the front of a yoke-like C-frame, the rearward extending arms of which are pinned to the tractor chassis.
Dozers nearly always operate under dirty conditions. Airborne dust, mud particles and the like collect on the machine and one place where such contaminants accumulate is on greasy surfaces including those of pivot assemblies. As a consequence, such assemblies are prone to accelerated wear. The machine manufacturer typically provides an external grease fitting (sometimes called a "zerk" fitting) at such assemblies for periodic greasing by the machine operator. Such fittings, and the grease passages associated with them, are arranged to inject grease directly into the slide-contact "interface" between the assembly outer race and the spherical bearing on which the race moves.
Such pivot assemblies are characterized by at least two disadvantages. One is that for continuing lubrication and reasonable assembly life (particularly in dirty operating environments--the usual case), the assembly must be lubricated frequently, e.g., every ten hours or so of operation. Experience has demonstrated that many machine users simply fail to follow the manufacturer's instructions in this regard.
Another disadvantage is that the lubricant passages (through the zerk fitting and connecting passages into the assembly) often become packed with a mixture of dirt and grease. Such mixture hardens and is difficult to remove--mere application of pressurized grease may well be insufficient to dislodge it. As a result, the machine operator may believe that s/he is effectively lubricating the assembly when, in fact, no fresh grease is being introduced to the vital sliding friction surfaces. Premature wear and failure result.
Examples of known pivot assemblies are shown in U.S. Pat. Nos. 3,645,340 (Frisbee) and 3,933,207 (Frisbee). The assembly shown in the Frisbee '340 patent has two open annular spaces, one each adjacent to the top and the bottom of the bearing-outer race sliding contact area. Such space permits dirt to enter such contact area. The assembly shown in the Frisbee '207 patent uses pliable seals to close such annular spaces and grease is introduced to the sliding contact area along a grease groove. While such seals exclude a certain amount of dirt, that which enters the spaces is trapped there. Both assemblies are mounted on the dozer C-frame by a pair of extended, generally parallel arms, one each above and below the assembly and neither assembly has provisions for continuous lubrication.
An improved joint assembly which extends the time interval at which greasing should be performed and which nevertheless provides for continuous lubrication of vital pivot assembly parts while obstructing entry of dust and dirt would be an important advance in the art.